The present invention pertains to a hydraulic mount, particularly adapted for motor vehicle applications, including a vacuum actuated decoupler operable to modify the dynamic stiffness of the mount.
Conventional automotive vehicle powertrain mounts exist in many variations and generally operate to provide engine vibration isolation while also controlling engine motion with respect to the vehicle frame or body structure. In many applications of engine and powertrain mounts, it is desirable to vary the dynamic stiffness of the mount to provide selective isolation of vibrations at certain frequencies related to engine speed, for example.
By way of example, for a four cylinder engine, the mount is desirably made to provide lower dynamic stiffness at the frequency of vibration related to the second order of engine speed (revolutions per minute). Accordingly, if the dynamic stiffness of the mount assembly can be varied and can be made lower than the static stiffness of the mount, improved vibration isolation can be obtained to reduce noise and vibration transmitted from the engine into the vehicle structure. It is to these ends that the present invention has been developed.
The present invention provides a mount, particularly adapted for automotive vehicle powertrain mount applications, which utilizes one or more decouplers which can be controlled to provide a lower dynamic stiffness of the mount assembly at predetermined frequencies to thereby provide improved vibration isolation between the structure supported by the mount and the structure supporting the mount.
In accordance with an important aspect of the present invention, a hydraulic engine mount is provided which is characterized by an elastomer body defining a fluid pumping chamber, a partition interposed the elastomer body and a fluid reservoir and an orifice track communicating hydraulic fluid between the pumping chamber and the reservoir. The reservoir is preferably delimited by a flexible diaphragm and the mount includes an elastomer type decoupler to aid in isolating relatively high frequency, low displacement vibrations. However, the decoupler may be modified in its performance characteristics by applying a vacuum to one side of the decoupler to modify the performance of the mount, particularly by substantially reducing the dynamic stiffness of the mount at predetermined vibration frequencies.
In accordance with another aspect of the present invention, a hydraulic type mount is provided which includes one or more active decouplers which may be controlled by solenoid operated valves, respectively, and a source of vacuum to modify the dynamic stiffness of the mount to isolate vibrations at particular frequencies. The decoupler or decouplers may be actuated at the same frequency as the vibrations being input to the mount and the phase angle of actuation of the decoupler may be selectively varied. The dynamic stiffness of the mount may be modified to be lower than the static stiffness to improve the vibration isolation characteristics of the mount, particularly for low amplitude relatively high frequency vibrations.
In accordance with still another aspect of the present invention, a hydraulic mount is provided which includes opposed pumping chambers and opposed vacuum actuated active decouplers which may be selectively actuated to provide for a wider range of stiffness of the mount at selected frequencies. For example, if the mount was supporting an engine that generates large second order shaking forces, the decouplers could vibrate in phase with these forces which would make the mount softer and operable to isolate such forces.